Larvae of the primitive lower termites are equipotent with respect to their developmental capabilities and, within a short time, as few as a dozen individuals can form an entire new colony complete with reproductives and soldiers. The reproductives of a termite colony produce pheromones, however, that normally inhibit the precocious sexual development of larvae into neotenic queens. These pheromones apparently influence endocrine glands and thus hormone titres: juvenile hormone will inhibit the development of neotenic queens (and stimulate soldier development). Despite much work, the termite queen phermone, which inhibits the development of neotonic reproductives, has never been isolated. The purpose of this proposal is to isolate and identify the termite queen pheromone, to determine where and when it is produced in the queen, and how it is obtained by larvae and dispersed throughout the colony. Preliminary studies of how the pheromone acts to influence the activity of the corpora allata, the endocrine source of juvenile hormone, will also be initiated. In future work, a knowledge of the pheromonal control of physiology and caste differentiation may contribute to an understanding of the mechanisms controlling gene expression during development.